Working Group Draft S. Probasco, Ed.
Internet-Draft B. Patil
Intended status: Informational August 30, 2012
Expires: March 3, 2013
Protocol to Access White Space database: PS, use cases and rqmtsdraft-ietf-paws-problem-stmt-usecases-rqmts-08
Abstract
Portions of the radio spectrum that are assigned to a particular use
but are unused or unoccupied at specific locations and times are
defined as "white space". The concept of allowing additional
transmissions (which may or may not be licensed) in white space is a
technique to "unlock" existing spectrum for new use. An obvious
requirement is that these additional transmissions do not interfere
with the assigned use of the spectrum. One approach to using the
white space spectrum at a given time and location is to verify with a
database for available channels.
This document describes a number of possible use cases of white space
spectrum and technology as well as a set of requirements for the
database query protocol. The concept of TV white spaces is described
including the problems that need to be addressed to enable white
space spectrum for additional uses without causing interference to
currently assigned use. Use of white space is enabled by querying a
database which stores information about the channel availability at
any given location and time.
Status of this Memo
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This Internet-Draft will expire on March 3, 2013.
Copyright Notice
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Internet-Draft PAWS: Problem, uses and requirements August 20121. Introduction1.1. Introduction to white space
Wireless spectrum is a commodity that is regulated by governments.
The spectrum is used for various purposes, which include but are not
limited to entertainment (e.g. radio and television), communication
(e.g. telephony and Internet access), military (e.g. radars etc.)
and, navigation (e.g. satellite communication, GPS). Portions of the
radio spectrum that are assigned to a licensed user but are unused or
unoccupied at specific locations and times are defined as "white
space". The concept of allowing additional transmissions (which may
or may not be licensed) in white space is a technique to "unlock"
existing spectrum for new use. An obvious requirement is that these
additional transmissions do not interfere with the assigned use of
the spectrum. One interesting observation is that often, in a given
physical location, the assigned user(s) may not be using the entire
band assigned to them. The available spectrum for additional
transmissions would then depend on the location of the additional
user. The fundamental issue is how to determine for a specific
location and specific time, if any of the assigned spectrum is
available for additional use. Academia and Industry have studied
multiple cognitive radio mechanisms for use in such a scenario. One
simple mechanism is to use a geospatial database that records the
assigned users occupation, and require the additional users to check
the database prior to selecting what part of the spectrum they use.
Such databases could be available on the Internet for query by
additional users.
Spectrum useable for data communications, especially wireless
Internet communications, is scarce. One area which has received much
attention globally is the TV white space: portions of the TV band
that are not used by broadcasters in a given area. In 2008 the
United States regulator (the FCC) took initial steps when they
published their first ruling on the use of TV white space, and then
followed it up with a ruling in 2010 [FCC Ruling] that established
the basic foundation for TV white space service in the US. In May
2012 the FCC issued minor updates further refining the previous
ruling [3MOO]. Finland passed an Act in 2009 enabling testing of
cognitive radio systems in the TV white space. The ECC has completed
Report 159 [ECC Report 159] containing requirements for operation of
cognitive radio systems in the TV white space. Ofcom published in
2004 their Spectrum Framework Review [Spectrum Framework Review] and
their Digital Dividend Review [DDR] in 2005, with proposals from 2009
onwards to access TV white space, leading to the 2011 Ofcom Statement
Implementing Geolocation [Ofcom Implementing] which has been followed
by draft requirements for TV white space devices [Ofcom
Requirements]. More countries are expected to provide access to
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their TV spectrum in similar ways. Any entity that is assigned
spectrum that is not densely used may be asked to give it up in one
way or another for more intensive use. Providing a mechanism by
which additional users share the spectrum with the assigned user is
attractive in many bands in many countries.
Television transmission until now has primarily been analog. The
switch to digital transmission has begun. As a result the spectrum
assigned for television transmission can now be more effectively
used. Unused channels and bands between channels can be used by
additional users as long as they do not interfere with the service
for which that channel is assigned. While urban areas tend to have
dense usage of spectrum and a number of TV channels, the same is not
true in semi-rural, rural and remote areas. There can be a number of
unused TV channels in such areas that can be used for other services.
Figure 1 shows TV white space within the lower UHF band:
Avg |
usage| |-------------- White Space
| | | | | |
0.6| || || V V ||
| || ||| | ||
0.4| || |||| | ||
| || |||| | ||<----TV transmission
0.2| || |||| | ||
|----------------------------------------
400 500 600 700 800
Frequency in MHz ->
Figure 1: High level view of TV White Space
The fundamental issue is how to determine for a specific location and
specific time if any of the spectrum is available for additional use.
There are two dimensions of use that may be interesting: space (the
area in which an additional user would not interfere with the
assigned use), and time: when the additional transmission would not
interfere with the assigned use. In this discussion, we consider the
time element to be relatively long term (e.g. hours in a day) rather
than short term (e.g. fractions of a second). Location in this
discussion is geolocation: where the transmitters (and sometimes
receivers) are located relative to one another. In operation, the
database records the assigned user's transmitter (and some times
receiver) locations along with basic transmission characteristics
such as antenna height, and power. Using rules established by the
local regulator, the database calculates an exclusion zone for each
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assigned user, and attaches a time schedule to that use. The
additional user queries the database with its location. The database
intersects the exclusion zones with the queried location, and returns
the portion of the spectrum not in any exclusion zone. Such methods
of geospatial database query to avoid interference have been shown to
achieve favorable results, and are thus the basis for rulings by the
FCC and reports from ECC and Ofcom. In any country, the rules for
which assigned entities are entitled to protection, how the exclusion
zones are calculated, and what the limits of use are by additional
users may vary. However, the fundamental notion of recording
assigned users, calculating exclusion zones, querying by location and
returning available spectrum (and the schedule for that spectrum) are
common.
This document includes the problem statement, use cases and
requirements associated with the use of white space spectrum by
secondary users via a database query protocol.
1.2. Scope1.2.1. In Scope
This document applies only to communications required for basic
service in TV white spaces. The protocol will enable a white space
radio device to complete the following tasks:
1. Determine the relevant white space database to query.
2. Connect to the database using a well-defined access method.
3. Register with the database using a well-defined protocol.
4. Provide its geolocation and perhaps other data to the database
using a well-defined format for querying the database.
5. Receive in response to the query a list of currently available
white space channels or frequencies using a well-defined format
for the information.
6. Send an acknowledgment to the database with information
containing channels selected for use by the device.
1.2.2. Out of Scope
The following topics are out of scope for this specification:
Co-existence and interference avoidance of white space devices
within the same spectrum
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Provisioning (releasing new spectrum for white space use)
2. Conventions and Terminology2.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2.2. Terminology
Database
In the context of white space and cognitive radio technologies,
the database is an entity which contains, but is not limited to,
current information as required by by the regulatory policies
about available spectrum at any given location and time, and other
types of related (to the white space spectrum) or relevant
information.
Device Class
Identifies classes of devices defined by Regional Regulators,
including fixed, mobile, portable, etc... May also indicate if
the device is indoor or outdoor.
Device ID
A unique number for each master device and slave device that
identifies the manufacturer, model number and serial number.
Location Based Service
An application or device which provides data, information or
service to a user based on their location.
Master Device
A device which queries the WS Database to find out the available
operating channels.
Protected Entity
An assigned user of white space spectrum which is afforded
protection against interference by additional users (white space
devices) for its use in a given area and time.
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Protected Contour
The exclusion area for a Protected Entity, held in the database
and expressed as a polygon with geospatial points as the vertices.
Slave Device
A device which uses the spectrum made available by a master
device, and cannot query the database directly.
TV White Space
TV white space refers specifically to radio spectrum which has
been allocated for TV broadcast, but is not occupied by a TV
broadcast, or other assigned user (such as a wireless microphone),
at a specific location and time.
TV White Space Device (TVWSD)
A White Space Device that operates in the TV bands.
White Space (WS)
Radio spectrum which is not fully occupied at a specific location
and time.
White Space Device (WSD)
A device which opportunistically uses some part of white space
spectrum. A white space device can be an access point, base
station, a portable device or similar. A white space device may
be required by local regulations to query a database with its
location to obtain information about available spectrum.
3. Prior Work3.1. The concept of Cognitive Radio
A cognitive radio uses knowledge of the local radio environment to
dynamically adapt its own configuration and function properly in a
changing radio environment. Knowledge of the local radio environment
can come from various technology mechanisms including sensing
(attempting to ascertain primary users by listening for them within
the spectrum), location determination and Internet connectivity to a
database to learn the details of the local radio environment. White
Space is one implementation of cognitive radio. Because a cognitive
radio adapts itself to the available spectrum in a manner that
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prevents the creation of harmful interference, the spectrum can be
shared among different radio users.
3.2. Background information on white space in the US
Television transmission in the United States has moved to the use of
digital signals as of June 12, 2009. Since June 13, 2009, all full-
power U.S. television stations have broadcast over-the-air signals in
digital only. An important benefit of the switch to all-digital
broadcasting is that it freed up parts of the valuable broadcast
spectrum. More information about the switch to digital transmission
is at [DTV].
Besides the switch to digital transmission for TV, the guard bands
that exist to protect the signals between stations can be used for
other purposes. The FCC has made this spectrum available for
unlicensed use and this is generally referred to as white space.
Please see the details of the FCC ruling and regulations in [FCC
Ruling]. The spectrum can be used to provide wireless broadband as
an example.
3.3. Background information on white space in the UK
Background information on white space in UK Since its launch in 2005,
Ofcom's Digital Dividend Review [DDR] has considered how to make the
spectrum freed up by digital switchover available for new uses,
including the capacity available within the spectrum that is retained
to carry the digital terrestrial television service. Similarly to
the US, this interleaved or guard spectrum occurs because not all the
spectrum in any particular location will be used for terrestrial
television and so is available for other services, as long as they
can interleave their usage around the existing users.
In its September 2011 Statement [Ofcom Implementing] Ofcom says that
a key element in enabling white space usage in the TV bands is the
definition and provision of a database which, given a device's
location, can tell the device which frequency channels and power
levels it is able to use without causing harmful interference to
other licensed users in the vicinity. Ofcom will specify
requirements to be met by such geolocation databases. It also says
that the technology has the possibility of being usefully applied
elsewhere in the radio spectrum to ensure it is used to maximum
benefit. For example, it may have potential in making spectrum
available for new uses following any switch to digital radio
services. Alternatively it may be helpful in exploiting some of the
public sector spectrum holdings. Ofcom will continue to consider
other areas of the radio spectrum where white space usage may be of
benefit.
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Internet-Draft PAWS: Problem, uses and requirements August 20123.4. Air Interfaces
Efforts are ongoing to specify air-interfaces for use in white space
spectrum. IEEE 802.11af, IEEE 802.15.4m and IEEE 802.22 are all
examples. Other air interfaces could be specified in the future such
as LTE.
4. Use cases and protocol services
There are many potential use cases that could be considered for the
TV white space spectrum. Providing broadband Internet access in
urban and densely populated hotspots, rural and underserved areas are
examples. Available channels may also be used to provide Internet
'backhaul' for traditional Wi-Fi hotspots, or by towns and cities to
monitor/control traffic lights or read utility meters. Still other
use cases include the ability to offload data traffic from another
Internet access network (e.g. 3G cellular network) or to deliver
location based services. Some of these use cases are described in
the following sections.
4.1. Protocol services
A complete protocol solution must provide all services that are
essential to enable the white space paradigm. Before a white space
device can begin operating it needs to know what channels are
available by sending a query to a white space database for a list of
available channels, the white space device must have the capability
to first locate or "discover" a suitable database. Additionally,
some regulatory authorities require the white space device to
register with the database as a first step. This section describes
the features required from the protocol.
4.1.1. White space database discovery
White space database discovery is preliminary to creating a radio
network using white space; it is a prerequisite to the use cases
below. The radio network is created by a master device. Before the
master device can transmit in white space spectrum, it must contact a
trusted database where the device can learn if any channels are
available for it to use. The master device will need to discover a
trusted database in the relevant regulatory domain, using the
following steps:
1. The master device is connected to the Internet by any means other
than using the white space radio. A local regulator may identify
exception cases where a master may initialize over white space
(e.g. the FCC allows a master to initialize over the TV white
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space in certain conditions).
2. The master device constructs and sends a service request over the
Internet to discover availability of trusted databases in the
local regulatory domain and waits for responses.
3. If no acceptable response is received within a pre-configured
time limit, the master device concludes that no trusted database
is available. If at least one response is received, the master
device evaluates the response(s) to determine if a trusted
database can be identified where the master device is able to
receive service from the database.
Optionally the radio device is pre-programmed with the Internet
address of at least one trusted database. The device can establish
contact with a trusted database using one of the pre-programmed
Internet addresses and establish a white space network (as described
in one of the following use cases).
Optionally the initial query will be made to a listing approved by
the national regulator for the domain of operation (e.g. a website
either hosted by or under control of the national regulator) which
maintains a list of WS databases and their Internet addresses. The
query results in the list of databases and their Internet addresses
being sent to the master, which then evaluates the response to
determine if a trusted database can be identified where the master
device is able to register and receive service from the database.
4.1.2. Device registration with trusted Database
Registration may be preliminary to creating a radio network using
white space; in some regulatory domains, for some device types, it is
a prerequisite to the use cases below. The radio network is created
by a master device. Before the master device can transmit in white
space spectrum, it must contact a trusted database where the device
can learn if any channels are available for it to use. Before the
database will provide information on available radio channels, the
master device must register with the trusted database. Specific
requirements for registration come from individual regulatory domains
and may be different.
Figure 2 shows an example deployment of this scenario.
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\|/ ----------
| |Database|
| .---. /---------
|-|---------| ( ) /
\|/ | Master | / \
| / | |========( Internet )
| / |-----------| \ /
+-|----+ (AirIF) ( )
|Master| / (----)
| | /
+------+
Figure 2: Example illustration of registration requirement in white
space use-case
A simplified operational scenario showing registration consists of
the following steps:
1. The master device must register with its most current and up-to-
date information. Typically the master device will register
prior to operating in white space for the first time after power
up, after changing location by a predetermined distance, and
after regular time intervals.
2. The master device shall provide to the database during
registration all information required according to local
regulatory requirements. This information may include, but is
not limited to, the Device ID, serial number assigned by the
manufacturer the device's location, device antenna height above
ground, name of the individual or business that owns the device,
name of a contact person responsible for the device's operation
address for the contact person, email address for the contact
person and phone number of the contact person.
3. The database shall respond to the registration request with an
acknowledgement code to indicate the success or failure of the
registration request. Additional information may be provided
according to local regulator requirements.
4.2. Use cases4.2.1. Hotspot: urban Internet connectivity service
In this use case Internet connectivity service is provided in a
"hotspot" to local users. Typical deployment scenarios include urban
areas where Internet connectivity is provided to local businesses and
residents, and campus environments where Internet connectivity is
provided to local buildings and relatively small outdoor areas. This
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deployment scenario is typically characterized by multiple masters
(APs or hotspots) in close proximity, with low antenna height, cells
with relatively small radius (a few kilometers or less), and limited
numbers of available radio channels. Many of the masters/APs are
assumed to be individually deployed and operated, i.e. there is no
coordination between many of the masters/APs. The masters/APs in
this scenario use a TDD radio technology. Each master/AP has a
connection to the Internet and may provide Internet connectivity to
other master and slave devices.
Figure 3 shows an example deployment of this scenario.
--------
|Device|\ \|/ ----------
| 1 | (TDD AirIF)\ | |Database|
-------- \ | (----) /---------
| \ |-|---------| ( ) /
| \| Master | / \
-------- /| |========( Internet )
|Device| /(TDD AirIF)/ |-----------| \ /
| 2 | / / ( )
------- / (----)
o | /
o | (TDD AirIF)
o | /
--------/
|Device|
| n |
--------
Figure 3: Hotspot service using TV white space spectrum
Once a master/AP has been correctly installed and configured, a
simplified power up and operation scenario utilizing TV White Space
to provide Internet connectivity service to slave devices, including
the ability to clear WSDs from select channels, is described. This
scenario consists of the following steps:
1. The master/AP powers up; however its WS radio and all other WS
capable devices will power up in idle/listen only mode (no
active transmissions on the WS frequency band). A local
regulator may identify exception cases where a master may
initialize over white space (e.g. the FCC allows a master to
initialize over TV white space in certain conditions).
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2. The master/AP has Internet connectivity, determines its location
(either from location determination capability or from saved
value that was set during installation), and establishes a
connection to a trusted white space database (see
Section 4.1.1).
3. The master/AP registers with the trusted database according to
regulatory domain requirements (see Section 4.1.2).
4. Following the successful registration process (if registration
is required), the master/AP will send a query to the trusted
database requesting a list of available WS channels based upon
its geolocation. The complete set of parameters to be provided
from the master to the database is specified by the local
regulator. Parameters may include WSD location, accuracy of
that location, device antenna height, device identifier of a
slave device requesting channel information.
5. If the master/AP has met all regulatory domain requirements
(e.g. been previously authenticated, etc), the database responds
with a list of available white space channels that the master
may use, and optionally a duration of time for their use,
associated maximum power levels or a notification of any
additional requirements for sensing.
6. Once the master/AP has met all regulatory domain requirements
(e.g. authenticated the WS channel list response message from
the database, etc), the AP selects one or more available WS
channels from the list. Prior to initiating transmission, if
required by local regulation, the master/AP informs the database
of the frequencies and power level it has chosen. This
reporting of the frequencies and power levels to the database is
repeated for each slave device that associated with the master.
7. The slave or user device scans the TV bands to locate a
master/AP transmission, and associates with the AP.
8. The slave/user device queries the master for a channel list. In
the query the slave/user device provides attributes that are
defined by local regulations. These may include the slaves'
Device ID and its geolocation.
9. Once the master/AP has met all regulatory domain requirements
(e.g. validating the Device ID with the trusted database, etc)
the master provides the list of channels locally available to
the slave/user device. Prior to initiating transmission, if
required by local regulation, the slave device informs the
master/AP of the frequencies and power level it has chosen, and
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the master/AP relays this information to the database.
10. The master sends an enabling signal to establish that the slave/
user device is still within reception range of the master. This
signal shall be encoded to ensure that the signal originates
from the master that provided the available list of channels.
11. Periodically, at an interval established by the local regulator,
the slave/user device must receive an enabling signal from the
master that provided the available list of channels or contact a
master to re-verify or re-establish the list of available
channels.
12. The master/AP must periodically repeat the process to request a
channel list from the database, steps 4 through 6 above. The
frequency to repeat the process is determined by the local
regulator. If the response from the database indicates a
channel being used by the master/AP is not available, the
master/AP must stop transmitting on that channel immediately.
In addition or optionally, the database may send a message to
the master/AP to rescind the availability of one or more
channels. The master/AP must stop transmitting on that channel
immediately.
13. The slave or user device must periodically repeat the process to
request a channel list from the master/AP, steps 8 and 9 above.
The frequency to repeat the process is determined by the local
regulator. If the response from the master/AP indicates that a
channel being used by the slave or user device is not available,
the slave or user device must stop transmitting on that channel
immediately. In addition or optionally, the database may send a
message to the master/AP to rescind the availability of one or
more channels. The master/AP must then notify the slave or user
device of the rescinded channels. The slave or user device must
stop transmitting on that channel immediately.
4.2.2. Wide-Area or Rural Internet broadband access
In this use case, Internet broadband access is provided as a Wide-
Area Network (WAN) or Wireless Regional Area Network (WRAN). A
typical deployment scenario is a wide area or rural area, where
Internet broadband access is provided to local businesses and
residents from a master (i.e., BS) connected to the Internet. This
deployment scenario is typically characterized by one or more fixed
master(s)/BS(s), cells with relatively large radius (tens of
kilometers, up to 100 km), and a number of available radio channels.
Some of the masters/BSs may be deployed and operated by a single
entity, i.e., there can be centralized coordination between these
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masters/BSs, whereas other masters/BSs may be deployed and operated
by operators competing for the radio channels where decentralized
coordination using the air-interface would be required. The BS in
this scenario uses a TDD radio technology and transmits at or below a
transmit power (EIRP) limit established by the local regulator. Each
base station has a connection to the Internet and may provide
Internet connectivity to multiple slaves/user devices. End-user
terminals or devices may be fixed or portable.
Figure 4 shows an example deployment of this scenario.
-------
|Slave|\ \|/ ----------
|Dev 1| (TDD AirIF) | |Database|
------- \ | .---. /----------
o \ |-|---------| ( ) /
o | Master | / \
o / | (BS) |========( Internet )
o / |-----------| \ /
------- (TDD AirIF) ( )
|Slave| / (----)
|Dev n|
-------
Figure 4: Rural Internet broadband access using TV white space
spectrum
Once the master/BS has been professionally installed and configured,
a simplified power up and operation scenario utilizing TV White Space
to provide rural Internet broadband access consists of the following
steps:
1. The master/BS powers up; however its WS radio and all other WS
capable devices will power up in idle/listen-only mode (no
active transmissions on the WS frequency band).
2. The master/BS has Internet connectivity, determines its location
(either from location determination capability or from a saved
value that was set during installation), and establishes a
connection to a trusted white space database (see
Section 4.1.1).
3. The master/BS registers with the trusted database service (see
Section 4.1.2). Meanwhile the DB administrator may be required
to store and forward the registration information to the
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regulatory authority. If a trusted white space database service
is not discovered, further operation of the WRAN may be allowed
according to local regulator policy (in this case operation of
the WRAN is outside the scope of the PAWS protocol).
4. Following the successful registration process (if registration
is required), the master/BS will send a query to the trusted
database requesting a list of available WS channels based upon
its geolocation. The complete set of parameters to be provided
from the master to the database is specified by the local
regulator. Parameters may include WSD identifier, location,
accuracy of that location, device antenna height, etc...
5. If the master/BS has been previously authenticated, the database
responds with a list of available white space channels that may
be used by the master/BS and optionally a maximum transmit power
(EIRP) for each channel, a duration of time the channel may be
used or a notification of any additional requirement for
sensing.
6. Once the master/BS authenticates the WS channel list response
message from the database, the master/BS selects an available WS
channel(s) from the list. Such selection may be improved based
on a set of queries to the DB involving a number of hypothetical
slave or user devices located at various locations over the
expected service area so that the final intersection of these
resulting WS channel lists allows the selection of a channel
that is likely available over the entire service area to avoid
potential interference at the time of slave/user terminal
association. The operator may also disallow some channels from
the list to suit local needs if required.
7. The slave or user device scans the TV bands to locate a WRAN
transmission, and associates with the master/BS.
8. In some regulatory domains, before a master device sends a
channel list, the slave/user device provides its geolocation to
the BS which, in turn, queries the database for a list of
channels available at the slave's geolocation.
9. Once this list of available channels is received from the
database by the master, the latter will decide, based on this
list of available channels and on the lists for all its other
associated slaves/user devices whether it should: a) continue
operation on its current channel if this channel is available to
all slaves/user devices, b) continue operation on its current
channel and not allow association with the new slave/user device
in case this channel is not available at its location or c)
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change channel to accommodate the new slave. In the latter
case, the master will notify all its associated slaves/user
devices of the new channel to which they have to move.
10. The master/BS must periodically repeat the process to request a
list of available channels from the database for itself and for
all its associated slaves/user devices. If the response from
the database indicates that the channel being used by the
master/BS is no longer available for its use, the master/BS must
indicate the new operating channel to all its slave/user
terminals, stop transmitting on the current channel and move to
the new operating channel immediately. If the channel that a
slave/user terminal is currently using is no longer included in
the list of locally available channels, the master may either
drop its association with the slave/user device so that this
device ceases all operation on its current channel or the master
may decide to move the entire cell to another channel to
accommodate the slave/user terminal and indicate the new
operating channel to all its slave/user devices before dropping
the link. The slave/user devices may then move to the
identified new operating channel or scan for another WRAN
transmission on a different channel. The frequency to repeat
the process is determined by the local regulator.
11. The slave/user device must transmit its new geographic location
every time it changes so that the repeated process described
under item 10 can rely on the most up-to-date geolocation of the
slave/user device.
4.2.3. Offloading: moving traffic to a white space network
In this use case internet connectivity service is provided over TV
white space as a supplemental or alternative datapath to a 3G or
other internet connection. In a typical deployment scenario an end
user has a primary internet connection such as a 3G cellular packet
data subscription. The user wants to use a widget or application to
stream video from an online service (e.g. youtube) to their device.
Before the widget starts the streaming connection it checks
connectivity options available at the current time and location.
Both 3G cellular data is available as well as TVWS connectivity (the
user is within coverage of a TVWS master -- hotspot, WAN, WRAN or
similar). The user may decide for many and various reasons such as
cost, RF coverage, data caps, etc. to prefer the TVWS connection over
the 3G cellular data connection. Either by user selection,
preconfigured preferences, or other algorithm, the streaming session
is started over the TVWS internet connection instead of the 3G
cellular connection. This deployment scenario is typically
characterized by a TVWS master/AP providing local coverage in the
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same geographical area as a 3G cellular system. The master/AP is
assumed to be individually deployed and operated, i.e. the master/AP
is deployed and operated by the user at his home or perhaps by a
small business such as a coffee shop. The master/AP has a connection
to the internet and provides internet connectivity to the slave/
end-user's device.
The figure below shows an example deployment of this scenario.
\|/
|
|
|-|---------|
| Master/AP |\
/| Router | \
Streaming/ |-----------| \
-------- / \ -----------
|Slave/| / \ (----) | Database|
|WS Dev| \ ( ) /----------
------- \ \ / \
\ X( Internet )
\ / \ /
Signaling \|/ / ( )\
\ | / (----) \----------
\ | / | YouTube|
\|-|---------| / ----------
| | /
| 3G BTS |/
|-----------|
Figure 5: Offloading: moving traffic to a white space network
Once a dual or multi mode device (3G + TVWS) is connected to a 3G
network, a simplified operation scenario of offloading selected
content such as video stream from the 3G connection to the TWVS
connection consists of the following steps:
1. The dual mode (or multi mode) device (3G + TVWS) is connected to
a 3G network. The device has located a TVWS master/AP operating
on an available channel and has associated or connected with the
TVWS master/AP.
2. The user activates a widget or application that streams video
from YouTube. The widget connects to YouTube over 3G cellular
data. The user browses content and searches for video
selections.
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3. The user selects a video for streaming using the widget's
controls. Before the widget initiates a streaming session, the
widget checks the available connections in the dual mode device
and finds a TVWS master/AP is connected.
4. Using either input from the user or pre-defined profile
preferences, the widget selects the TVWS master/AP as the
connection to stream the video.
4.2.4. White space serving as backhaul
In this use case Internet connectivity service is provided to users
over a more common wireless standard such as Wi-Fi with white space
entities providing backhaul connectivity to the Internet. In a
typical deployment scenario an end user has a device with a radio
such as Wi-Fi. An Internet service provider or a small business
owner wants to provide Wi-Fi Internet connectivity service to their
customers. The location where Internet connectivity service via
Wi-Fi is to be provided is within the coverage area of a white space
master (e.g. Hotspot or Wide-Area/Rural network). The service
provider installs a white space slave device and connects it to the
Wi-Fi access point(s). Wi-Fi access points with an integrated white
space slave component may also be used. This deployment scenario is
typically characterized by a WS master/AP/BS providing local
coverage. The master/AP has a connection to the Internet and
provides Internet connectivity to slave devices that are within its
coverage area. The WS slave device is 'bridged' to a Wi-Fi network
thereby enabling Internet connectivity service to Wi-Fi devices. The
WS Master/AP/BS which has some form of Internet connectivity (wired
or wireless) queries the database and obtains available channel
information. It then provides service using those channels to slave
devices which are within its coverage area.
Figure 6 shows an example deployment of this scenario.
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\|/ white \|/ \|/ Wi-Fi \|/
| space | | |
| | | |-|----|
|--------| |-|---------| |-|------|-| | Wi-Fi|
| | | Master | | Slave | | Dev |
|Internet|------| (AP/BS) | | Bridge | |------|
| | | | | to Wi-Fi |
|--------| |-----------| |----------| \|/
|
|-|----|
| Wi-Fi|
| Dev |
|------|
Figure 6: WS for backhaul
Once the bridged device (WS + Wi-Fi) is connected to a master and WS
network, a simplified operation scenario of backhaul for Wi-Fi
consists of the following steps:
1. A bridged device (WS + Wi-Fi) is connected to a master device
operating in the WS spectrum. The bridged device operates as a
slave device in either Hotspot or Wide-Area/Rural Internet use
cases described above.
2. Once the slave device is connected to the master, the Wi-Fi
access point has Internet connectivity as well.
3. End users attach to the Wi-Fi network via their Wi-Fi enabled
devices and receive Internet connectivity.
4.2.5. Rapid deployed network for emergency scenario
Organizations involved in handling emergency operations often have a
fully owned and controlled infrastructure, with dedicated spectrum,
for day to day operation. However, lessons learned from recent
disasters show such infrastructures are often highly affected by the
disaster itself. To set up a replacement quickly, there is a need
for fast reallocation of spectrum, where in certain cases spectrum
can be cleared for disaster relief. To utilize unused or cleared
spectrum quickly and reliably, automation of allocation, assignment
and configuration is needed. A preferred option is to make use of a
robust protocol, already adopted by radio manufacturers. This
approach does in no way imply such organizations for disaster relief
must compete on spectrum allocation with other white spaces users,
but they can. A typical network topology would include wireless
access links to the public Internet or private network, wireless ad
hoc network radios working independent of a fixed infrastructure and
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its current location, other parameters required by the local
regulator (see Section 4.2.1, step 4) and a prediction of its
future location. The current location is specified in latitude
and longitude. The method to specify the future location is
TBD, potential methods include movement vector (direction and
velocity), a set of latitude/longitude points which specify a
closed polygon where the future location is within the polygon,
or similar.
5. If the mobile master has met all regulatory domain requirements
(e.g. been previously authenticated, etc), the database responds
with a list of available white space channels that the mobile
master may use, and optional information which may include (1) a
duration of time for the use of each channel (2) a maximum
transmit power for each channel and (3) notification of any
additional requirement for sensing.
6. Once the mobile master has met all regulatory domain
requirements (e.g. authenticated the WS channel list response
message from the database, etc), the master selects one or more
available WS channel(s) from the list for use. At this point
the mobile master may begin direct communication with another
mobile master using methods outside the scope of PAWS.
7. The slave/user device scans to locate a mobile master
transmission, and associates with the mobile master.
8. The slave/user device queries the master for a channel list,
providing to the master the slave's device identification, and
optionally its geolocation and a prediction of its future
location.
9. Once the mobile master has met all regulatory domain
requirements (e.g. the slave's device identification is verified
by the database), the mobile master provides the list of
channels locally available to the slave/user device.
10. If the mobile master moves outside the predicted range of future
positions in step 4, it must repeat the process to request a
channel list from the database, steps 4 through 6 above. If the
response from the database indicates a channel being used by the
mobile master is not available, the master/AP must stop
transmitting on that channel immediately.
11. The slave or user device must periodically repeat the process to
request a channel list from the master/AP, steps 8 and 9 above.
The frequency to repeat the process is determined by the local
regulator. If the response from the master/AP indicates that a
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channel being used by the slave or user device is not available,
the slave or user device must stop transmitting on that channel
immediately. In addition or optionally, the database may send a
message to the master/AP to rescind the availability of one or
more channels. The master/AP must then notify the slave or user
device of the rescinded channels. The slave or user device must
stop transmitting on that channel immediately.
4.2.7. Indoor Networking
In this use case, the users are inside a house or office. The users
want to have connectivity to the Internet or to equipment in the same
or other houses / offices. This deployment scenario is typically
characterized by master devices within buildings, that are connected
to the Internet using a method that does not utilize whitespace. The
master devices can establish whitespace links between themselves, or
between themselves and one or more user devices.
Figure 9 shows an example deployment of this scenario.
\|/
|
+-------+ |
|TVWS |\ +-|---------+
|Usr Dev| WS AirIF \ | TVWS |\
+-------+ X|Master Dev | \
/ +-----------+ \
+-------+ WS AirIF | \ +----------+
|TVWS |/ | \ (----) | Database |
|Usr Dev| | \ ( ) /----------+
+-------+ WS AirIF \ / \
| X( Internet )
| / \ /
+-------+ \|/ | / ( )
|TVWS |\ | | / (----)
|Usr Dev| WS AirIF | | /
+-------+ \ +-|---------+ /
\ | TVWS | /
|Master Dev |/
+-----------+
Figure 9: Example illustration of indoor TV white space use-case
A simplified operational scenario utilizing TV whitespace to provide
indoor networking consists of the following steps:
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1. The master device powers up with its whitespace radio in idle or
listen mode only (no active transmission on the whitespace
frequency band).
2. The master device has Internet connectivity, determines its
location (either from location determination capability or from a
saved value that was set during installation), and establishes a
connection to a trusted white space database (see Section 4.1.1).
3. The master device registers with the trusted database according
to regulatory domain requirements (see Section 4.1.2).
4. Following the successful registration process (if registration is
required), the master device sends a query to the trusted
database requesting a list of available WS channels based upon
its geolocation. The complete set of parameters to be provided
from the master to the database is specified by the local
regulator. Parameters may include WSD location, accuracy of that
location, device antenna height, device identifier of a slave
device requesting channel information.
5. If the master has met all regulatory requirements, the database
responds with a list of available white space channels that the
master device may use, and optional information which may include
inter alia (1) a duration of time for the use of each channel
(channel validity time) (2) a maximum radiated power for each
channel, and (3) directivity and other antenna information.
6. Once the master device authenticates the whitespace channel list
response message from the database, the master device selects one
or more available whitespace channels from the list. At this
point the mobile master may begin direct communication with
another mobile master using methods outside the scope of PAWS.
7. The user device(s) scan(s) the white space bands to locate the
master device transmissions, and associates with the master.
4.2.8. Machine to Machine (M2M)
In this use case, each "machine" includes a white space slave device
and can be located anywhere, fixed or on the move. Each machine
needs to have connectivity to the Internet and or to other machines
in the vicinity. Machine communication over a TVWS channel, whether
to a master device or to another machine (slave device), is under the
control of a master device. This deployment scenario is typically
characterized by a master device with Internet connectivity by some
connection that does not utilize TV white space.
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that the master device may use, and optional information which
may include inter alia (1) a duration of time for the use of each
channel (channel validity time) (2) a maximum radiated power for
each channel or a notification of any additional requirements for
sensing.
6. Once the master device authenticates the whitespace channel list
response message from the database, the master device selects one
or more available whitespace channels from the list.
7. The slave devices fitted to the machines scan the TV bands to
locate the master transmissions, and associate with the master
device.
8. Further signaling can take place outside scope of PAWS to
establish direct links among those slave devices that have
associated with the same master device. At all times these
direct links are under the control of the master device. For
example, common to all use cases, there may be a regulatory
requirement for transmissions from slave to master to cease
immediately if so requested by the master, or if connection to
the master is lost for more than a specified period of time.
When one of these conditions occurs, transmissions from slave to
slave would also cease. Various mechanisms could be used to
detect loss of signal from the master, for example by requiring
masters to transmit regular beacons if they allow slave to slave
communications. Direct slave to slave transmissions could only
restart if each slave subsequently restores its connection to the
same master, or each slave joins the network of another master.
5. Problem Statement
The use of white space spectrum is enabled via the capability of a
device to query a database and obtain information about the
availability of spectrum for use at a given location. The databases
are reachable via the Internet and the devices querying these
databases are expected to have some form of Internet connectivity,
directly or indirectly. The databases may be country specific since
the available spectrum and regulations may vary, but the fundamental
operation of the protocol should be country independent.
An example high-level architecture of the devices and white space
databases is shown in Figure 11:
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-----------
| Master |
|WS Device| ------------
|Lat: X |\ .---. /--------|Database X|
|Long: Y | \ ( ) / ------------
----------- \-------/ \/ o
( Internet ) o
----------- /------( )\ o
| Master | / ( ) \
|WS Device|/ (_____) \ ------------
|Lat: X | \--------|Database Y|
|Long: Y | ------------
-----------
Figure 11: High level view of the White space database architecture
In Figure 11, note that there could be multiple databases serving
white space devices. The databases are country specific since the
regulations and available spectrum may vary. In some countries, for
example, the U.S., the regulator has determined that multiple,
competing databases may provide service to White Space Devices.
A messaging interface between the white space devices and the
database is required for operating a network using the white space
spectrum. The following sections discuss various aspects of such an
interface and the need for a standard. Other aspects of a solution
including provisioning the database, and calculating protected
contours are considered out of scope of the initial effort, as there
are significant differences between countries and spectrum bands.
5.1. Global applicability
The use of TV white space spectrum is currently approved by the FCC
in the United States. However regulatory bodies in other countries
are also considering similar use of available spectrum. The
principles of cognitive radio usage for such spectrum is generally
the same. Some of the regulatory details may vary on a country
specific basis. However the need for devices that intend to use the
spectrum to communicate with a database remains a common feature.
The database provides a known, specifiable Protection Contour for the
primary user, not dependent on the characteristics of the White Space
Device or its ability to sense the primary use. It also provides a
way to specify a schedule of use, because some primary users (for
example, wireless microphones) only operate in limited time slots.
Devices need to be able to query a database, directly or indirectly
over the public Internet and/or private IP networks prior to
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operating in available spectrum. Information about available
spectrum, schedule, power, etc. are provided by the database as a
response to the query from a device. The messaging interface needs
to be:
1. Radio/air interface agnostic - The radio/air interface technology
used by the white space device in available spectrum can be IEEE
802.11af, IEEE 802.15.4m, IEEE 802.16, IEEE 802.22, LTE etc.
However the messaging interface between the white space device
and the database should be agnostic to the air interface while
being cognizant of the characteristics of various air-interface
technologies and the need to include relevant attributes in the
query to the database.
2. Spectrum agnostic - the spectrum used by primary and secondary
users varies by country. Some spectrum has an explicit notion of
a "channel" a defined swath of spectrum within a band that has
some assigned identifier. Other spectrum bands may be subject to
white space sharing, but only have actual frequency low/high
parameters to define protected entity use. The protocol should
be able to be used in any spectrum band where white space sharing
is permitted.
3. Globally applicable - A common messaging interface between white
space devices and databases will enable the use of such spectrum
for various purposes on a global basis. Devices can operate in
any country where such spectrum is available and a common
interface ensures uniformity in implementations and deployment.
Since the White Space Device must know its geospatial location to
do a query, it is possible to determine which database, and which
rules, are applicable, even though they are country specific.
4. Address regulatory requirements - Each country is likely to have
regulations that are unique to that country. The messaging
interface needs to be flexible to accommodate the specific needs
of a regulatory body in the country where the white space device
is operating and connecting to the relevant database.
5.2. Database discovery
Another aspect of the problem space is the need to discover the
database. A white space device needs to find the relevant database
to query, based on its current location or for another location.
Since the spectrum and databases are country specific, the device
will need to discover the relevant database. The device needs to
obtain the IP address of the specific database to which it can send
queries in addition to registering itself for operation and using the
available spectrum.
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A protocol that enables a white space device to query a database to
obtain information about available channels is needed. A device may
be required to register with the database with some credentials prior
to being allowed to query. The requirements for such a protocol are
specified in this document.
5.4. Data model definition
The contents of the queries and response need to be specified. A
data model is required which enables the white space device to query
the database while including all the relevant information such as
geolocation, radio technology, power characteristics, etc. which may
be country and spectrum and regulatory dependent. All databases are
able to interpret the data model and respond to the queries using the
same data model that is understood by all devices.
Use of XML for specifying a data model is an attractive option. The
intent is to evaluate the best option that meets the need for use
between white space devices and databases.
6. Requirements6.1. Normative Requirements
D. Data Model Requirements:
D.1: The Data Model MUST support specifying the location of the
WSD, the uncertainty in meters, the height & its
uncertainty, and confidence in percentage of the location
determination. The Data Model MUST support both North
American Datum of 1983 and WGS84.
D.2: The Data Model MUST support specifying the regulatory domain
and its corresponding data requirements.
D.3: The Data Model MUST support specifying an ID of the
transmitter device. This ID would contain the ID of the
transmitter device that has been certified by a regulatory
body for its regulatory domain. The Data Model MUST support
a device class. The Data Model MUST support specifying
information about the type of RAT of the transmitter device.
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D.4: The Data Model MUST support specifying a manufacturer's
serial number for a white space device.
D.5: The Data Model MUST support specifying the antenna and
radiation related parameters of the subject, such as:
antenna height
antenna gain
maximum output power, EIRP (dBm)
antenna radiation pattern (directional dependence of the
strength of the radio signal from the antenna)
spectrum mask with lowest and highest possible frequency
spectrum mask in dBr from peak transmit power in EIRP,
with specific power limit at any frequency linearly
interpolated between adjacent points of the spectrum mask
measurement resolution bandwidth for EIRP measurements
D.6: The Data Model MUST support specifying owner and operator
contact information for a transmitter. This includes the
name of the transmitter owner, name of transmitter operator,
postal address, email address and phone number of the
transmitter operator.
D.7: The Data Model MUST support specifying spectrum
availability. Spectrum units are specified by low and high
frequencies and may have an optional channel identifier.
The Data Model MUST support a schedule including start time
and stop time for spectrum unit availability. The Data
Model MUST support maximum power level for each spectrum
unit.
D.8: The Data Model MUST support specifying channel availability
information for a single location and an area (e.g. a
polygon defined by multiple location points or a geometric
shape such as a circle).
D.9: The Data Model MUST support specifying the frequencies and
power levels selected for use by a device in the
acknowledgement message.
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P. Protocol Requirements:
P.1: The protocol MUST provide a mechanism to enable WSD
discovery. In some environments, a listing of the approved
white space databases is maintained by the national
regulator. The protocol MUST support discovery of a
database using a listing approved by a national regulator.
P.2: The address of a database (e.g. in form of a URI) can be
preconfigured in a master device. The master device MUST
be able to contact a database using a pre-configured
database address.
P.3: The protocol MUST support determination of regulatory
domain governing its current location.
P.4: The protocol MUST provide the ability for the database to
authenticate the master device.
P.5: The protocol MUST provide the ability for the master device
to verify the authenticity of the database with which it is
interacting.
P.6: The messages sent by the master device to the database and
the messages sent by the database to the master device MUST
support integrity protection.
P.7: The protocol MUST provide the capability for messages sent
by the master device and database to be encrypted.
P.8: The protocol MUST support the master device registering
with the database.
P.9: The protocol MUST support a registration acknowledgement
including appropriate result codes.
P.10: The protocol MUST support a channel query request from the
master device to the database. The channel query request
message MUST include parameters as required by local
regulatory requirement. These parameters MAY include any
of the parameters and attributes required to be supported
in the Data Model Requirements.
P.11: The protocol MUST support a channel query response from the
database to the master device. The channel query response
message MUST include parameters as required by local
regulatory requirement. These parameters MAY include any
of the parameters and attributes required to be supported
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in the Data Model Requirements.
P.12: The protocol MUST support a channel usage message from the
master device to the database. The channel usage message
MUST include parameters as required by local regulatory
requirement for the master and its associated slaves.
These parameters MAY include any of the parameters and
attributes required to be supported in the Data Model
Requirements.
P.13: The protocol MUST support a channel usage message
acknowledgement.
P.14: The protocol MUST support a validation request from the
master to the database to validate a slave device. The
validation request MUST include the slave device ID.
P.15: The protocol MUST support a validation response from the
database to the master to indicate if the slave device is
validated by the WSDB. The validation response MUST
include a response code.
P.16: The protocol between the master device and the database
MUST support the capability to change channel availability
information on short notice.
P.17: The protocol between the master device and the database
MUST support a channel availability request which specifies
a geographic location as an area as well as a point.
6.2. Non-normative requirements
O. Operational Requirements:
O.1: The database and the master device MUST be connected to the
Internet.
O.2: A master device MUST be able to determine its location
including uncertainty and confidence level. A fixed master
device MAY use a location programmed at installation or have
the capability to determine its location to the required
accuracy. A mobile master device MUST have the capability to
determine its location to the required accuracy.
O.3: The master device MUST identify a database to which it will
register, make channel requests, etc... The master device MAY
select a database for service by discovery at runtime or the
master device MAY select a database for service by means of a
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pre-programmed URI address.
O.4: The master device MUST implement at least one connection
method to access the database. The master device MAY contact
a database directly for service (e.g. as defined by FCC) or
the master device MAY contact a listing server first followed
by contact to a database (e.g. as defined by Ofcom).
O.5: The master device MUST obtain an indication about the
regulatory domain governing operation at its current location,
i.e. the master device MUST know if it operates under
regulations from FCC, Ofcom, etc...
O.6: The master device MAY register with the database according to
local regulatory policy. Not all master devices will be
required to register. Specific events will initiate
registration, these events are determined by regulator policy
(e.g. at power up, after movement, etc...). When local
regulatory policy requires registration, the master device
MUST register with its most current and up-to-date
information, and MUST include all variables mandated by local
regulator policy.
O.7: A master device MUST query the database for the available
channels based on its current location before starting radio
transmission in white space. Parameters provided to the
database MAY include device location, accuracy of the
location, antenna characteristic information, device
identifier of any slave device requesting channel information,
etc...
O.8: The database MUST respond to an available channel list request
from an authenticated and authorized device and MAY also
provide time constraints, maximum output power, start and stop
frequencies for each channel in the list and any additional
requirements for sensing.
O.9: According to local regulator policy, a master device MAY
inform the database of the actual frequency usage of the
master and its slaves. The master MUST include parameters
required by local regulatory policy, e.g. device ID,
manufacturer's serial number, channel usage and power level
information of the master and its slaves.
O.10: After connecting to a master device's radio network a slave
device MUST query the master device for a list of available
channels. The slave MUST include parameters required by local
regulatory policy, e.g. device ID, device location.
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O.11: According to local regulatory policy, the master device MAY
query the database with parameters received from the slave
device.
O.12: The database MUST respond to a query from the master device
containing parameters from a slave device.
O.13: A master device MUST repeat the query to the database for the
available channels as often as required by the regulation
(e.g., FCC requires once per day) to verify that the operating
channels continue to remain available.
O.14: A master device which changes its location more than a
threshold distance (specified by local regulatory policy)
during its operation, MUST query the database for available
operating channels each time it moves more than the threshold
distance (e.g., FCC specifies 100m) from the location it
previously made the query.
O.15: According to local regulator policy, a master device may
contact a database via proxy service of another master device.
O.16: A master device MUST be able to query the whitespace database
for channel availability information for a specific expected
coverage area around its current location.
O.17: A Master device MUST include its unique identity in all
message exchanges with the database.
6.3. Guidelines
The current scope of the working group is limited and is reflected in
the requirements captured in Section 6.1. However white space
technology itself is expected to evolve and address other aspects
such as co-existence and interference avoidance, spectrum brokering,
alternative spectrum bands, etc. The design of the data model and
protocol should be cognizant of the evolving nature of white space
technology and consider the following set of guidelines in the
development of the data model and protocol:
1. The data model SHOULD provide a modular design separating out
messaging specific, administrative specific, and spectrum
specific parts into separate modules.
2. The protocol SHOULD support determination of which administrative
specific and spectrum specific modules are used.
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Internet-Draft PAWS: Problem, uses and requirements August 20127. IANA Considerations
This document has no requests to IANA.
8. Security Considerations
Threat model for the PAWS protocol
Assumptions:
It is assumed that an attacker has full access to the network medium
between the master device and the white space database. The attacker
may be able to eavesdrop on any communications between these
entities. The link between the master device and the white space
database can be wired or wireless and provides IP connectivity.
It is assumed that both the master device and the white space
database have NOT been compromised from a security standpoint.
Threat 1: User modifies a device to masquerade as another valid
certified device
Regulatory environments require that devices be certified and
register in ways that accurately reflect their certification.
Without suitable protection mechanisms, devices could simply
listen to registration exchanges, and later registering claiming
to be those other devices. Such replays would allow false
registration, violating regulatory regimes. A white space
database may be operated by a commercial entity which restricts
access only to authorized users. A master device MAY need to
identify itself to the database and be authorized to obtain
information about available channels.
Threat 2: Spoofed white space database
A master device discovers a white space database(s) through which
it can query for channel information. The master device needs to
ensure that the white space database with which it communicates
with is an authentic entity. The white space database needs to
provide its identity to the master device which can confirm the
validity/authenticity of the database. An attacker may attempt to
spoof a white space database and provide responses to a master
device which are malicious and result in the master device causing
interference to the primary user of the spectrum.
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Threat 3: Modifying a query request
An attacker may modify the query request sent by a master device
to a white space database. The attacker may change the location
of the device or the capabilities in terms of its transmit power
or antenna height etc. which could result in the database
responding with incorrect information about available channels or
max transmit power allowed. The result of such an attack is that
the master device would cause interference to the primary user of
the spectrum. It could also result in a denial of service to the
master device by indicating that no channels are available.
Threat 4: Modifying a query response
An attacker could modify the query response sent by the white
space database to a master device. The channel information or
transmit power allowed type of parameters carried in the response
could be modified by the attacker resulting in the master device
using channels that are not available at a location or
transmitting at a greater power level than allowed resulting in
interference to the primary user of that spectrum. Alternatively
the attacker may indicate no channel availability at a location
resulting in a denial of service to the master device.
Threat 5: Unauthorized use of channels by an uncertified device
An attacker may be a master device which is not certified for use
by the relevant regulatory body. The attacker may listen to the
communication between a valid master device and white space
database and utilize the information about available channels in
the response message by utilizing those channels. The result of
such an attack is unauthorized use of channels by a master device
which is not certified to operate. The master device querying the
white space database may be operated by a law-enforcement agency
and the communications between the device and the database are
intended to be kept private. A malicious device should not be
able to eavesdrop on such communications.
Threat 6: Third party tracking of white space device location and
identity
A white space database in a regulatory domain may require a master
device to provide its identity in addition to its location in the
query request. Such location/identity information can be gleaned
by an eavesdropper and used for tracking purposes. A master
device may prefer to keep the location/identity information hidden
from eavesdroppers, hence the protocol should provide a means to
protect the location and identity information of the master device
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and prevent tracking of locations associated with a white space
database query. When the master device sends both its identity
and location to the DB, the DB is able to track it. If a
regulatory domain does not require the master device to provide
its identity to the white space database, the master device may
decide not to send its identity, to prevent being tracked by the
DB.
Threat 7: Malicious individual acts as a PAWS entity (spoofing DB or
as MiM) to terminate or unfairly limit spectrum access of devices for
reasons other than incumbent protection
A white space database MAY include a mechanism by which service
and channels allocated to a master device can be revoked by
sending an unsolicited message. A malicious node can pretend to
be the white space database with which a master device has
registered or obtained channel information from and send a revoke
message to that device. This results in denial of service to the
master device.
Threat 8: Natural disaster resulting in inability to obtain
authorization for white space spectrum use by emergency responders
In the case of a sizable natural disaster a lot of Internet
infrastructure ceases to function. Emergency services users need
to reconstitute quickly and will rely on establishing radio WANs.
The potential for lot of radio WAN gear that has been unused
suddenly needs to be pressed into action. And the radio WANs need
frequency authorizations to function. Regulatory entities may
also authorize usage of additional spectrum in the affected areas.
The white space radio entities may need to establish communication
with a database and obtain authorizations. In cases where
communication with the white space database fails, the white space
devices cannot utilize white space spectrum. Emergency services,
which require more spectrum precisely at locations where network
infrastructure is malfunctioning or overloaded, backup
communication channels and distributed white space databases are
needed to overcome such circumstances. Alternatively there may be
other mechanisms which allow the use of spectrum by emergency
service equipment without strict authorization or with liberal
interpretation of the regulatory policy for white space usage.
The security requirements arising from the above threats are captured
in the requirements of section 6.1.
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Internet-Draft PAWS: Problem, uses and requirements August 20129. Summary and Conclusion
Wireless spectrum is a scarce resource. As the demand for spectrum
grows, there is a need to more efficiently utilize the available and
allocated spectrum. Cognitive radio technologies enable the
efficient usage of spectrum via means such as sensing or by querying
a database to determine available spectrum at a given location for
opportunistic use. White space is the general term used to refer to
the bands within the spectrum which is available for secondary use at
a given location. In order to use this spectrum a device needs to
query a database which maintains information about the available
channels within a band. A protocol is necessary for communication
between the devices and databases which would be globally applicable.
The document describes some examples of the role of the white space
database in the operation of a radio network and also shows examples
of services provided to the user of a TVWS device. From these use
cases, requirements are determined. These requirements are to be
used as input to the definition of a Protocol to Access White Space
database (PAWS).
10. Acknowledgements
The authors acknowledge Gabor Bajko, Teco Boot, Nancy Bravin, Rex
Buddenberg, Gerald Chouinard, Stephen Farrell, Michael Fitch, Joel M.
Halpern, Jussi Kahtava, Paul Lambert, Brian Rosen, Andy Sago, Peter
Stanforth, John Stine and, Juan Carlos Zuniga for their contributions
to this document.
11. References11.1. Normative References
[802.11p] IEEE, "IEEE Standard for Information technology -
Telecommunications and information exchange between
systems - Local and metropolitan area networks - Specific
requirements; Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications; Amendment
6: Wireless Access in Vehicular Environments; http://standards.ieee.org/getieee802/download/802.11p-2010.pdf",
July 2010.
[802.22] IEEE, "IEEE Standard for Information technology -
Telecommunications and information exchange between
systems - Wireless Regional Area Networks (WRAN) -
Specific requirements; Part 22: Cognitive Wireless RAN
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